Power amplifiers, such as the types of power amplifiers used in wireless communication systems, must be capable of operating at various power levels based on instructions from a controller. A typical prior art power amplifier uses individual pins to control the various functions of the power amplifier. A typical power amplifier may receive signals relating to what band the power amplifier is operating in, and a control signal to control when the power amplifier turns on. A power amplifier may also receive an analog automatic power control signal APC having a power level proportional to the desired output power level.
One problem with prior art power amplifiers is that the their functionality is limited. For example, limitations in the prior art prohibit some features, such as the ability to integrate new functions, or the ability for other devices to read the status of the power amplifier.
Another problem in the prior art relates to controlling the output power of power amplifiers. When the designer of a wireless communication device (e.g., a cellular phone) implements any particular power amplifier with their design, a great amount of effort is required to design ramp profiles for use in controlling the output power of a power amplifier. The characteristics of a desired ramp profile depend on several factors including characteristics of the power amplifier being used, temperature, and battery voltage. As a result, designers typically must design new ramp profiles for every specific design.